This invention relates to an endoscope.
An endoscope comprises a body, an insertion portion extending from the body, a bending portion extending from a front end of the insertion portion, and a rigid tip member mounted on a front end of the bending portion. The bending portion is remotely operated or bent by manipulating a manipulation member mounted on the body.
Generally, the insertion portion comprises a spiral member, a first braid mounted around the spiral member, and a first protective tube mounted around the first braid. Generally, the bending portion comprises a row of ring-shaped segments pivotally connected to one another, a second braid mounted around the row of ring-shaped segments, and a second protective tube mounted around the second braid. The foremost one of the row of segments is fixedly secured to the tip member, and the rearmost segment is connected to the spiral member of the insertion portion via a connecting ring.
The insertion portion, though flexible or soft, needs to have a certain degree of rigidity. If the insertion portion is too soft, it is contracted upon receipt of an axial compression force, so that the insertion portion fails to advance along a body cavity. On the other hand, the bending portion need to be more flexible than the insertion portion, because the bending portion is required to be bent into a large angle with a relatively small manipulating force from the manipulation member. For this reason, the second braid is softer than the first braid, and the second protective tube is softer than the first protective tube.
Generally, the front end of the first protective tube and the rear end of the second protective tube are held in contact with each other at the outer peripheral surface of the above-mentioned connecting ring. Each of these protective tubes is fixedly secured to the connecting ring by a yarn wound on the end of the protective tube.
In the endoscope of an above general construction, the relatively rigid insertion portion and the relatively soft bending portion are directly connected together, so that a point of abrupt change in rigidity exists in this connection portion. Therefore, when the portion of connection between the bending portion and the insertion portion is abutted against a curved portion of a body cavity of a patient during the insertion of the endoscope into the body cavity, the front end portion of the insertion portion close to the connection portion can not be bent smoothly, thus giving a pain to the patient.
In an endoscope disclosed in Japanese Laid-Open Utility Model Application No. 55-112505, an insertion portion and a bending portion have a common protective tube. This protective tube comprises two layers made respectively of soft resins. The resin of the inner layer is softer than the resin of the outer layer. The outer layer is thickest at its proximal end adjacent to a body, and is decreasing in thickness progressively toward its distal end. On the other hand, the inner layer is thinnest at its proximal end, and is increasing in thickness progressively toward its distal end. The sum of the thicknesses of the two layers is uniform over the entire length of the protective tube. With the use of this protective tube, the rigidity over the area from the insertion portion to the bending portion continuously varies, and therefore it is thought that the insertion of the endoscope into a body cavity can be carried out smoothly, thus giving less pain to the patient. However, the use of such a protective tube increases the cost of a endoscope. Further, a relatively long portion of the protective tube close to the distal end is soft, and therefore the slack of this relatively long portion is increased by the repeated wiping and rinsing of the protective tube after the diagnosis and by the repeated bending of the bending portion by the manipulation member. This slack gives a pain to the patient when the bending portion and the insertion portion are to be inserted into the body cavity.
Japanese Laid-Open Utility Model Application No. 63-77003 discloses an endoscope related to the present invention. In this endoscope, a second protective tube of a bending portion covers the entire outer periphery of a connecting ring connecting a spiral member of an insertion portion to a rear segment of the bending portion, and the rear end portion of this second protective tube extends slightly rearwardly from the connecting ring. At a position rearwardly of and adjacent to the connecting ring, the rear end portion of the second protective tube of the bending portion, as well as a front end portion of a first protective tube of the insertion portion, is fixedly secured to the outer periphery of a first braid of the insertion portion. This fixing is effected by winding a yarn on the outer peripheries of the end portions of the first and second protective tubes. In this endoscope, since the rear end portion of the second protective tube is fixed at a position adjacent to the connecting ring, the front end portion of the insertion portion (which is disposed rearwardly of the connection portion) is not softer than the other portion of the insertion portion. Therefore, this endoscope does not have the advantages of the present invention.